Network topologies for long armature linear motor multi-car elevator systems
Çetin, Gökalp (2020) Network topologies for long armature linear motor multi-car elevator systems. [Thesis]
Long armature linear motor is an example of a distributed control system with a large number of motor drivers spread in a linear fashion. Having multiple movers on the same motor increases the level of complication while adding a new challenge to the control and network aspects of it. In such a system, there is no room for error on the communication between nodes, as the motor drivers must be accurate despite delay and packet loss. Although delay and packet loss in communication networks are almost unavoidable, reducing these disadvantages by choosing a suitable network topology with accompanying communication protocol is possible. In this thesis, Ethernet, CANBUS and EtherCAT protocols have been tested for their suitability for a reliable real-time communication protocol to be used on control systems while being implemented on three different network topologies taking three different approaches to the same problem. These topologies are introduced for the communication of motor drivers and sensor nodes of long armature linear motor with multiple elevator cars. Topology G with its global approach, is a system containing motor drivers spread linearly, a main computer to plan and coordinate the motion of the linear motor movers and a gateway computer in between. The structure of this topology, with its simplicity introduces a bandwidth problem having over a certain number of motor drivers. Due to this, some of the sensor nodes messages collide and packets drop while running multiple elevator cars simultaneously. Unlike Topology G, Topology L is a hierarchical system with a more localized approach, consisting of motor drivers, gateway computers that group motor drivers into small networks, and a main computer connecting to every gateway computer with an outer network. Thanks to the structure of this topology, increasing the number of motor driver nodes is not increasing each individual network load. Finally, Topology R with an unorthodox method uses a completely different network structure yet, successfully utilizes gateways to group motor drivers and other nodes, similar to Topology L does, so that increasing the number of motor drivers does not affect the overall load on the network. The proposed topologies are simulated on MATLAB Simulink using TrueTime, a toolbox for simulation of distributed real-time control systems. As creating such a system with multiple networks and many nodes connected to those networks is a re-iterative task, instead of using Simulink as its graphical user interface (GUI) with drag and drop method, we used MATLAB scripts to create and modify the Simulink models which also allowed us to easily change parameters and test various cases recording and analyzing the responses of the system. The advantages and disadvantages of all topologies are explained in detail with examples of some test cases, comparing the performance of them based on reliability and delay amount. The results indicate that when compared the three, Topology L with a local approach and Topology R with a ring approach have a better performance with higher reliability and nominal delay than Topology G. Therefore, either Topology L or Topology R is suggested for the communication of motor drivers of long armature linear motor with multiple elevator cars.
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